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Androgens and oestrogens in normal and cryptorchid stallions
Journal of Reproduction and Fertility. Supplement
|October 1, 1975
Summary
Bilateral cryptorchid stallions had higher estrogens and lower androgens. Seasonal and daily variations in androgens were observed, with rapid clearance post-castration and increased levels after sexual stimulation.
Area of Science:
- Reproductive endocrinology
- Equine physiology
Background:
- Understanding stallion reproductive endocrinology is crucial for managing breeding programs and diagnosing reproductive disorders.
- Cryptorchidism, a condition where testes fail to descend, can impact hormone production and reproductive capacity in stallions.
Purpose of the Study:
- To investigate the hormonal profiles (total androgens, testosterone, total estrogens) in stallions with varying testicular status, including cryptorchidism.
- To explore the influence of diurnal variation, season, castration, and sexual stimulation on androgen levels in stallions.
Main Methods:
- Hormone levels (total androgens, testosterone, total estrogens) were measured in intact, unilaterally cryptorchid, bilaterally cryptorchid stallions, and geldings.
- Blood samples were analyzed to determine hormone concentrations and variations.
- Identification of specific androgens in spermatic vein blood and epididymal fluid.
Main Results:
- Bilateral cryptorchid stallions exhibited significantly higher total estrogens and lower total androgens compared to other groups.
- Significant diurnal variations in total androgen levels were recorded.
- A seasonal effect was observed, with decreased androgen and testosterone levels during winter in both intact and thyroidectomized animals.
- Androgen levels decreased rapidly after castration, becoming undetectable within 12 hours.
- Sexual stimulation appeared to elevate total androgen levels.
- Testosterone, androstenedione, dihydrotestosterone, androstandiols, and androstenediol were identified in spermatic vein blood; dihydrotestosterone was found in cauda epididymidis fluid.
Conclusions:
- Testicular status, particularly bilateral cryptorchidism, significantly influences androgen and estrogen levels in stallions.
- Androgen production in stallions is subject to diurnal rhythms, seasonal changes, and external stimuli like sexual activity.
- The rapid clearance of androgens post-castration highlights the primary role of the testes in their production.